<!DOCTYPE html>
<html lang="zh-CN">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <script>
        alert("Hello JavaScript!")
    </script>
    <input type="button" value="点我一下" onclick="alert('haha')">
</body>

</html>